Chelsea have completed the signing of Holland defender Khalid Boulahrouz. He joins from Hamburg for an undisclosed fee. The 24-year-old passed a medical examination and agreed personal terms at Stamford Bridge over the weekend.

Despite an indifferent World Cup, in which his most memorable contribution was an outrageous thigh-high challenge on Cristiano Ronaldo during Holland's now infamous second-round clash with Portugal, Boulahrouz comes to England with a glowing reputation. He was imperious in Germany last season, when Hamburg finished third with the best defensive record in the Bundesliga.

One of Boulahrouz's greatest assets is his versatility, as he can play right across the back. "In a short squad and in a country where you can have only 16 players for a match, it's important to have cover for many positions," said Chelsea manager Jose Mourinho. "So, for example, now I can have Boulahrouz, Ricardo [Carvalho] and John [Terry] - three options for the centre; I can have Paulo [Ferreira] and Boulahrouz - two options for the right side; I can have Boulahrouz and Wayne Bridge - two options for the left side."

It is perhaps significant that Mourinho's explanation makes no mention of William Gallas. One of Chelsea's top performers last season, the French defender has been at loggerheads with the club all summer. He is said to be frustrated both at being deployed at left-back when he feels he is better in the centre, and at being paid less than some squad members who have never featured as regularly as him.

Reports in France claim his morale "is at its lowest possible level" and that he is determined to leave the club. Arsenal are reportedly keen to sign him, either as part of an eventual Ashley Cole transfer to Stamford Bridge or as a straightforward cash deal.